USA – Scientists from Michigan State University (MSU) have uncovered new insights into how low levels of water contamination affect fish behavior and survival.
Published in the prestigious journals Environmental Science & Technology and Environmental Toxicology and Chemistry, this groundbreaking research sheds light on how pollutants like methylmercury (MeHg) and polychlorinated biphenyl (PCB126) can alter fish behavior, growth, and gene expression, even in species that have developed some tolerance to pollution.
The team, led by Cheryl Murphy, a professor in MSU’s Department of Fisheries and Wildlife and director of the MSU Center for PFAS Research, focused on the Atlantic killifish, a species known for its ability to adapt to industrial pollution.
Collaborating with scientists from the U.S. Environmental Protection Agency and other institutions, they compared the responses of two populations: one that had evolved to tolerate contaminants and one that had not.
Surprisingly, even the evolved population exhibited changes in gene expression and behavior when exposed to low contaminant levels.
Murphy’s findings challenge the assumption that pollution-tolerant species are unaffected by low-level exposure.
“People assume that fish that have evolved tolerance will be fine, but we’re showing that they’re only able to survive, not thrive,” said Murphy. “There’s still an impact on gene expression and behavior, even in these adapted populations.”
One key discovery was the identification of specific behavioral changes linked to gene expression alterations.
According to Janice Albers, a former MSU doctoral student and current U.S. Geological Survey fish biologist, this study marks a significant advance in understanding how contaminants influence fine-scale behavior patterns.
Traditional behavioral studies often relied on gross measurements like average swimming speed, but the team’s innovative approach allowed them to detect more nuanced behavioral shifts.
This breakthrough provides a clearer link between specific genes and behaviors, offering a deeper understanding of how pollution impacts fish at both the individual and population levels.
Understanding these behavioral changes is crucial for ecological risk assessments, as they can be early indicators of larger population-level effects.
Lori Ivan, a senior research associate at MSU, emphasized the importance of studying individual fish to predict broader impacts on entire populations.
“By the time a whole population is affected, the damage is often already done,” Ivan noted. “Our goal in ecotoxicology is to use sub-organismal behavioral data to make predictions about population outcomes before it’s too late.”
The research also explored whether zebrafish, a common model organism in toxicology studies, can serve as a reliable surrogate for other fish species like yellow perch and Atlantic killifish.
The results showed that zebrafish responses were not representative of the other species, underscoring the need for species-specific studies when assessing the effects of contaminants.
Murphy’s team concluded that accounting for uncertainties in modeling fish behavior and population outcomes is critical for producing more accurate risk assessments.
“Incorporating uncertainty gives us a more protective estimate of risk, ensuring that we’re not underestimating the potential impacts,” Murphy explained.
This research offers a powerful new framework for linking gene expression, behavior, and population dynamics in fish exposed to waterborne contaminants.
The team hopes their work will inspire further studies and lead to improved methods for assessing environmental risks, with implications for managing endangered species and preserving aquatic ecosystems.
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